Many chemical or biochemical reaction systems utilize a solid phase as a feed material substrate or reagent. In most cases, such materials are size-reduced prior to introduction to the reactor so that there is a significant amount of interacting surface available. For some systems, the surface interactions may ultimately use up available reactants on the substrate surface and, thus, result in a significant reduction in the overall rate of reaction. This is certainly the case for the enzymatic hydrolysis of cellulose in lignocellulosic solids by cellulase enzymes. What is needed is a periodic or continuous replenishment of fresh substrate surface on the solid particulates so that a high rate of reaction can be maintained.
It has been shown that the use of additional attrition during the course of enzymatic cellulose hydrolysis can materially enhance the reaction rate and yield. The most successful demonstration of attrition was carried out in a small reactor in which large rotating paddles were used to continuously stir a bed of steel balls within the reactor chamber. The moving steel balls provided sufficient shear force to continue to attrit the solid cellulosic particles and provide fresh substrate surfaces for enzymatic attack. The reaction rate was enhanced, but unfortunately, it is very difficult to scale-up such a reactor concept since the paddles that move the steel balls around become progressively larger, heavier, more expensive, and require much greater power as the reactor becomes larger.
In order to further elucidate attrition reactor technology, the following publications are suggested:
1. Neilson, M. J., et al, Biotechnol. Bioeng. 24, 293 (1982). PA0 2. Ryu, S. K., and Lee, J. M., Biotechnol. Bioeng. 25, 53 (1983). PA0 3. Deeble, M. F., and Lee, J. M., Biotechnol. Bioeng. 15, 277 (1985). PA0 4. Jones, E. O., and Lee, J. M., Biotechnol. Bioeng, 31, 35 (1988).